Search found 48 matches
- Wed Mar 10, 2021 4:02 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Understanding Kinetics
- Replies: 10
- Views: 565
Re: Understanding Kinetics
Make sure you understand reaction orders! Then definitely know which orders correspond to which integrated rate laws (and graphs) and half life equations.
- Wed Mar 10, 2021 3:57 pm
- Forum: General Rate Laws
- Topic: Intermediate
- Replies: 59
- Views: 3839
Re: Intermediate
As stated above, intermediates are produced and then consumed in multi-step reactions. Therefore, they can be canceled out when writing the overall reaction. Also, make sure that you can distinguish intermediates from catalysts. While they both cancel out in the overall reaction, catalysts are the r...
- Wed Mar 10, 2021 3:53 pm
- Forum: General Rate Laws
- Topic: Final Exam
- Replies: 19
- Views: 813
Re: Final Exam
Does anyone know if the majority of questions will be focused on electrochemistry and kinetics since we haven't been tested on them yet?
- Wed Mar 10, 2021 3:52 pm
- Forum: General Rate Laws
- Topic: slow step
- Replies: 7
- Views: 362
Re: slow step
In lecture today, I believe Lavelle said that the slow step is what determines the overall reaction rate/rate of formation. Also, if the early step is fast, and the later step is slow, then there is a bottleneck where a buildup of intermediate results in the first step being at about equilibrium, so...
- Wed Mar 10, 2021 3:48 pm
- Forum: General Rate Laws
- Topic: intermediates in rate laws
- Replies: 5
- Views: 257
Re: intermediates in rate laws
Does it ever make sense to include intermediates in a rate law? Would you include them for the rate laws of elementary steps?
- Sun Mar 07, 2021 11:20 am
- Forum: Zero Order Reactions
- Topic: Overall order of the reaction
- Replies: 45
- Views: 2008
Re: Overall order of the reaction
Finding the overall order of the reaction is simple once you determine the individual orders! You can simply sum up the individual orders. For example, if you have a 1st order and 2nd order reaction, the overall would be 3 because 1+2=3.
- Sun Mar 07, 2021 11:16 am
- Forum: General Rate Laws
- Topic: Instantaneous versus Average rate [ENDORSED]
- Replies: 3
- Views: 247
Re: Instantaneous versus Average rate [ENDORSED]
Also, the instantaneous rate is the change at the particular moment or the gradient at that point, while the average rate is the rate over a range of time.
- Sun Mar 07, 2021 11:08 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Units for reaction rates
- Replies: 15
- Views: 1127
Re: Units for reaction rates
Will these always be the units for 0, 1st, 2nd reaction rates? Or is there any circumstance where they could change?
- Sun Mar 07, 2021 11:04 am
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox
- Replies: 16
- Views: 915
Re: Balancing Redox
After identifying the half reaction and balancing all elements, you can identify the total oxidation charge on both sides of each half reaction. Add the appropriate number of electrons to the side that has a more positive charge so that both sides become equal. Do this for both half reactions. Then ...
- Sun Mar 07, 2021 10:49 am
- Forum: Balancing Redox Reactions
- Topic: Oxidizing Agent
- Replies: 33
- Views: 1325
Re: Oxidizing Agent
The table that we have been using for homework problems gives reduction potentials. So, the element with the highest potential is most likely to be reduced, also making it the best oxidizing agent.
- Thu Feb 25, 2021 4:10 pm
- Forum: Balancing Redox Reactions
- Topic: sapling q.3
- Replies: 2
- Views: 154
Re: sapling q.3
You need to convert from acidic solution (H+) to basic solution (OH-) by adding enough OH- ions to both sides so that all H+ ions can combine with them to form water, which you will now have on both sides. Cancel the appropriate number so it only appears on one side.
- Thu Feb 25, 2021 4:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Writing Cell diagrams
- Replies: 4
- Views: 262
Re: Writing Cell diagrams
Quick question: does it matter what species comes first in writing the cell diagrams? I know that the cathode will be on the right of the double line and the anode reaction will be on the left of the double lines, but does it matter where we put each species? For instance: Are these essentially the...
- Thu Feb 25, 2021 4:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 30
- Views: 1422
Re: Salt Bridge
Does the salt bridge have anything to do with changing the mass of the electrodes of a voltaic cell? Or is change in mass only a result of the change from a solid to aqueous solution?
- Thu Feb 25, 2021 3:58 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing Agent and Reducing Agent
- Replies: 7
- Views: 409
Re: Oxidizing Agent and Reducing Agent
I have another question to follow up on oxidizing and reducing agents. When determining these agents, do we use the single element or the entire compound that this element is a part of? Hopefully that makes sense??
- Thu Feb 25, 2021 3:55 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation states
- Replies: 2
- Views: 174
Re: oxidation states
There are ordered rules that we use in order to assign an oxidation state to each element. Because the third rule states that "in their compounds, group-1 metals have an oxidation state of +1..." we would start by assigning K an oxidation state of +1. Rule 6 then states that oxygen atoms n...
- Sun Feb 21, 2021 3:35 pm
- Forum: Balancing Redox Reactions
- Topic: cell vs electrode vs half reaction
- Replies: 6
- Views: 481
Re: cell vs electrode vs half reaction
Funmi Baruwa wrote:so cells represent the reaction?
In a way, yes, since the cell is made up of the two electrodes, with the cathode representing reduction and the anode representing oxidation. Together, these half-cells carry out a redox reaction for the entire cell.
- Sun Feb 21, 2021 3:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Ecell vs Eocell
- Replies: 7
- Views: 562
Re: Ecell vs Eocell
Alex Benson wrote:Ecell is the cell potential, whereas Eocell is at the standard conditions.
To add on, these standard conditions are 1M solution or 1 atm at 25 degrees Celsius (298 K).
- Sun Feb 21, 2021 3:26 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Spontaneous Reduction
- Replies: 9
- Views: 561
Re: Spontaneous Reduction
All Lavelle mentioned in lecture regarding spontaneous reduction was that if your standard reduction potential value is positive, the reaction is spontaneous.
- Sun Feb 21, 2021 2:44 pm
- Forum: Balancing Redox Reactions
- Topic: Anode and Cathode
- Replies: 11
- Views: 568
Re: Anode and Cathode
In a galvanic cell, the anode side is oxidized because electrons flow towards the cathode, which is the reduced side.
- Sun Feb 21, 2021 2:41 pm
- Forum: Balancing Redox Reactions
- Topic: salt bridge
- Replies: 19
- Views: 776
Re: salt bridge
The salt bridge connects oxidation and reduction half-cells to maintain neutrality within the circuit. This neutrality is important for the reactions to carry out.
- Sat Feb 13, 2021 1:16 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Entropy
- Replies: 27
- Views: 1167
Re: Entropy
In terms of Lavelle's exams, do we think the most important thing to know about entropy is a simple definition and how it relates to phase changes (solid, liquid, gas)?
- Sat Feb 13, 2021 1:14 pm
- Forum: Van't Hoff Equation
- Topic: Vant Hoff's equation
- Replies: 7
- Views: 510
Re: Vant Hoff's equation
The Van't Hoff Equation can be used to calculate K at different temperatures if delta H is known.
- Sat Feb 13, 2021 1:05 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Gibbs Free Energy
- Replies: 8
- Views: 511
Re: Standard Gibbs Free Energy
Is it always true that if delta G is negative, the reaction is spontaneous? If so, please explain!
- Sat Feb 13, 2021 1:01 pm
- Forum: Student Social/Study Group
- Topic: Classes for next quarter?
- Replies: 165
- Views: 16385
Re: Classes for next quarter?
Would it be a bad idea to take 14C and BL at the same time? Chem is definitely not my strongest subject. Any suggestions??
- Sat Feb 13, 2021 12:59 pm
- Forum: Student Social/Study Group
- Topic: Thoughts on Upcoming Midterm 2
- Replies: 41
- Views: 1741
Re: Thoughts on Upcoming Midterm 2
Unfortunately, I didn't do very well on midterm 1, so the pressure is on for midterm 2. I mostly studied using the textbook homework problems and sapling. Does anyone who did well have a strategy or study method that worked best for them? Thanks!
- Fri Feb 05, 2021 1:15 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed Systems
- Replies: 14
- Views: 650
Re: Closed Systems
I don't believe Lavelle ever mentioned applying pressure when talking about closed systems. I think that all we need to know is that in a closed system, there is no matter exchanged with the surroundings, only energy.
- Fri Feb 05, 2021 1:07 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Temperature vs Enthalpy
- Replies: 6
- Views: 339
Re: Temperature vs Enthalpy
Heat is a transfer of energy due to a temperature difference. Enthalpy is the change in amount of heat in a system at constant pressure. You can only use heat and enthalpy interchangeably if there is no work being done to the system
- Fri Feb 05, 2021 1:03 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Examples for types of systems
- Replies: 8
- Views: 316
Re: Examples for types of systems
Open system: exchange of matter and energy (heat) with surroundings
Closed: no matter exchanged, only energy exchanged with surroundings
Isolated: no exchange of matter or energy with surroundings
I know these are definitions not examples, but it helps a lot with identifying systems!
Closed: no matter exchanged, only energy exchanged with surroundings
Isolated: no exchange of matter or energy with surroundings
I know these are definitions not examples, but it helps a lot with identifying systems!
- Tue Feb 02, 2021 2:18 pm
- Forum: Calculating Work of Expansion
- Topic: What is V1 and V2
- Replies: 12
- Views: 773
Re: What is V1 and V2
If we have an initial volume of zero, would using the formula, w=nRT*ln(V2/V1) ever work?
- Tue Feb 02, 2021 2:16 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling Week 3/4 #18
- Replies: 2
- Views: 156
Re: Sapling Week 3/4 #18
Our constants and formulas sheet gives Cp=(5/2)R and Cv=(3/2)R. However for this question, the Cp=(7/2)R and Cv=(5/2)R. Does this mean the two are always related by subtracting 1R from Cp?
- Sun Jan 31, 2021 3:42 pm
- Forum: Calculating Work of Expansion
- Topic: Integral vs Infinite Sum [ENDORSED]
- Replies: 3
- Views: 215
Re: Integral vs Infinite Sum [ENDORSED]
Im pretty sure that Lavelle only included the infinite sum relation with work/pressure/delta volume to set up his explanation of the derivation of the integral equation. Since the integral is basically the sum with infinitely small segments, I don't quite see a situation where it would be better to...
- Sun Jan 31, 2021 3:39 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: isolated system
- Replies: 16
- Views: 886
Re: isolated system
Is there any way to change the energy of an isolated system?
- Sun Jan 31, 2021 3:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: perfect system
- Replies: 20
- Views: 853
Re: perfect system
In a perfect system, qsys+qsur=0 since qsys=-qsur. This means that the heat gained by the system is lost by the surroundings, or vice versa, explaining the opposite signs. The phenomena is explained by the First Law of Thermodynamics, which states that heat is neither lost nor destroyed, only transf...
- Sun Jan 31, 2021 3:32 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity vs. Specific Heat
- Replies: 7
- Views: 299
Re: Heat Capacity vs. Specific Heat
I understand that specific heat is more useful than heat capacity because it is an intensive property, but does this mean that we will probably never be using heat capacity in this class?
- Sun Jan 31, 2021 3:30 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Neutralization
- Replies: 25
- Views: 1079
Re: Neutralization
Does this mean that the salt and the water are both neutral solutions (pH=7)?
- Sun Jan 24, 2021 10:36 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Difference between Strong and Weak acids and bases
- Replies: 3
- Views: 210
Re: Difference between Strong and Weak acids and bases
In what kind of problem would we need use this distinction in order to solve?
- Sun Jan 24, 2021 10:28 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat released/ gained
- Replies: 22
- Views: 1065
Re: Heat released/ gained
Breaking a bond requires energy, so this reaction is endothermic. Forming a bond releases energy, so it is exothermic.
- Sun Jan 24, 2021 10:27 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: calorimetry
- Replies: 9
- Views: 659
Re: calorimetry
Do different calorimeters each have their own specific heat capacities?
- Sun Jan 24, 2021 10:18 am
- Forum: Phase Changes & Related Calculations
- Topic: No Heat Change
- Replies: 15
- Views: 583
Re: No Heat Change
So to clarify, heat is not synonymous with temperature in this case? Heat is increasing but temperature is not?
- Sun Jan 24, 2021 10:14 am
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic v. Exothermic
- Replies: 139
- Views: 14484
Re: Endothermic v. Exothermic
Delta H represents the change in enthalpy, which is the total heat content of a system. So yes, the positive or negative sign of delta H should be used to determine whether a reaction is endothermic or exothermic. When it is less than zero, this means that heat has been released from the system, ind...
- Sun Jan 17, 2021 12:30 pm
- Forum: General Science Questions
- Topic: Conjugate Acids and Bases
- Replies: 4
- Views: 214
Re: Conjugate Acids and Bases
How would we determine if something is neutral given its conjugate? I'm pretty sure it has something to do with salts, but I'm still confused.
- Sun Jan 17, 2021 12:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between ionization and protonation
- Replies: 5
- Views: 808
Re: Difference between ionization and protonation
In the Week 2 sapling assignment, #5 asks us to find the % protonation. I got it wrong at first because I just used the initial concentration of B as the denominator, but the solution tells us to use the formal concentration, which is the sum of the concentrations of B and BH+. Can anyone explain wh...
- Fri Jan 15, 2021 8:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When x is negligible in Equilibrium constant
- Replies: 34
- Views: 1557
Re: When x is negligible in Equilibrium constant
If we determine that K is less than 10^-3 or, to be safe, less than 10^-4, but get an x greater than 5%, does that mean that we had a mathematical error when calculating our K? Or are we simply unable to use approximation for that particular problem?
- Wed Jan 13, 2021 10:26 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chem Equilibria
- Replies: 6
- Views: 324
Re: Chem Equilibria
Hi, I know this is probably a pretty simple answer, but could someone reiterate how Q is different than K? I'm still a bit confused.
- Fri Jan 08, 2021 10:31 am
- Forum: Ideal Gases
- Topic: Reading the textbook
- Replies: 262
- Views: 150895
Re: Reading the textbook
Does anyone who has taken Lavelle's class in the past recommend reading the textbook consistently? Do the types of questions in the book appear on the midterms or final? Thank you!
- Fri Jan 08, 2021 10:27 am
- Forum: Administrative Questions and Class Announcements
- Topic: Registering/Creating Your Chemistry Community Account
- Replies: 40
- Views: 101011
Re: Registering/Creating Your Chemistry Community Account
MackenziePerillo-1L wrote:Does it matter what our alias is?
They recommended using our name and discussion section :) I'm assuming that makes it easier for them to give us points?
- Fri Jan 08, 2021 10:23 am
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Assignments
- Replies: 30
- Views: 1938
Re: Sapling Assignments
Are the questions that say they are due the Sunday of Week 2 the only graded homework for this course? Is everything else provided just optional/recommended/extra practice?
- Fri Jan 08, 2021 10:20 am
- Forum: Administrative Questions and Class Announcements
- Topic: Accessing the E-textbook [ENDORSED]
- Replies: 125
- Views: 32510
Re: Accessing the E-textbook [ENDORSED]
I purchased the sapling+ 7th edition ebook a few days ago from ucla and have not received a notification for the prepaid code to access sapling. Does anybody have a solution or are in a similar situation? Thanks. Hi, I had the exact same problem, because I did not previously take 14A with Lavelle. ...